I did the faces stuff only once and it was very quick and very dirty. So I just exported all idf/emb (morph & heads) of the one I wanted, mass renamed to the one that's got to be replaced. Imported them, added the erp file of the one I wanted into the assetgroup file of the one that's got to be replaced.
iirc in the end you just need to change one emb file and a few idfs, but I stopped at that point, because I never had a serious intention about it - I was only curious if you could use heads from the interviewer and if Calderon was easy going on a female body